CLDN1 and neoplasm: Moreover, the membrane zinc importer ZIP4 was found to be overexpressed in human pancreatic cancer and promotes tumor growth and metastasis, and it was demonstrated that ZIP4 represses claudin-1 through a ZEB1-dependent transcriptional mechanism, which leads to activation of FAK and paxillin to cause increased cell migration, invasion and tumor metastasis (147, 148).